If you had looked a few threads down this question was answered already.

For the sake of being on topic, Elemental Force IS affected by our mastery. I can't give you a definitive answer as to which one is the better enchant, however for my shaman, Elemental Force was simming to be about a 2k DPS increase over Windsong.

is it the same for the haste build though? (EM+PE) since our mastery will be way lower.

I've had far better results going with a mastery build and Elemental Force to answer your question. However, that is just my personal experience. Naturally, if you're going for a haste build Elemental Force will not be hitting as hard and might not be that much better than Windsong, but with mastery it's far greater. I really need to get my hands on some Dancing Steel though soon.